Air conditioning is key to navigating climate change

Record sustained high temperatures this summer across Europe, the United States and other parts of the world have brought into focus both the benefits and challenges of a global society increasingly dependent on air conditioning. In places where air conditioning is unusual or nonexistent, record-shattering heat is taking a deadly toll.

In much of the United States, air conditioning is fairly ubiquitous, however. The technology grew and developed here in critical ways, and helped shape the politics and history of the United States itself. Its spread across the country — early in Washington, D.C., and then across the South and Sun Belt — helped to transform the movement of Americans and regional distribution of political and economic power since World War II. This history shows how changes in the built environment have contributed to the climate crisis and points to the urgency of transforming our buildings to mitigate the effects.

Initially in the early 20th century, air conditioning was developed in the United States to increase economic productivity, by making industrial workplaces and then public spaces such as movie theaters more comfortable for workers and consumers.

This extended to Capitol Hill, where, beginning in the 1920s, Congress, after much debate, appropriated funds for the air conditioning of the U.S. Capitol and nearby House and Senate office buildings. Air conditioning transformed the annual cycle of congressional activity. Before air conditioning, a session of Congress typically lasted for less than 300 days, adjourning by the end of June for the summer. The city was largely deserted from mid-June to September, even in periods of national crisis. In years after 1938, when air conditioning became operational throughout Capitol Hill, Congress carried its sessions past 300 days and beyond the end of June, when heat waves settled over Washington. Air conditioning curtailed calls for early adjournment.

Air conditioning also transformed daily bureaucratic life in buildings such as the Pentagon, which had the world’s largest airconditioning plant in a single structure when it opened in 1943. By the 1950s, the General Services Administration found that productivity in government offices increased by 9.5 percent when air conditioning was installed. In Washington, where peak temperatures of 106 degrees and 60 percent humidity had been recorded, air conditioning, “far from being a mere luxury,” proved “essential for normal operating efficiency of personnel.”

The experience of Washington’s many federal employees with air conditioning on the job was a key factor in raising demand for it in other settings, including department stores, theaters, hotels and other commercial sites seeking to draw more consumers.

The rationing of electric power and equipment during World War II initially slowed local adoption of air conditioning in the nation’s capital. But as early as 1942, the area’s Potomac Electric Power Co. (now Pepco) became the nation’s first summer-peaking utility, meaning that more electricity was used in summer to support air conditioning than was used in winter to power heating equipment. By 1953, Washington had more air conditioning per capita than any other American city. In 1966, about 56 percent of Pepco’s residential customers, including those in the Washington suburbs, had air conditioning of some type; by 1981, that number had risen to nearly 90 percent.

Washington’s transformation anticipated air conditioning’s effects across the South and the Sun Belt. Its capacity to mitigate the effects of Southern climate made the South and Southwest attractive for industrial and related demographic growth, shifting economic and political power from its traditional centers on the East Coast and in the Midwest. It made intolerably hot places in the summer habitable and made some of them, from Southern California to Florida, attractive to retirees, new whitecollar industries and other year-round newcomers. Improving the indoor environment with air conditioning also enabled the lengthening of the Southern school year by addressing, as one observer noted in 1946, “Unquestionably, one of the largest single obstacles to greater educational advancement in the Deep South.” That is, “the physical conditions under which the faculty and pupils must work.”

In 1940, the most populous states were New York, Pennsylvania and Illinois. Swelling populations in Florida, Texas and California made these the three most populous states by 2015.